Lets see, the Civil War began 156 years ago and according to you in people in the 22nd century should not judge the mortality of Hitler, Stalin, and Pol Pot.
After all, how could they judge the morality of those who lived in the 20th century?
With the state of the world right now it is easy to think that one or all of the three, Hitler, Stalin, and Pol Pot may be seen by those in the 22nd century as the greatest of all time. That is if we don't win against the Godless Globalists or Devilish Islam.
You or I can have no idea what the future may think just as we should temper our understanding of the 19th century with the standards and views of their time.